Linux/AM4378: boot from for AM4378x, no signal from CLK and Data pin after boot.

Part Number:AM4378

Tool/software: Linux

Hi, 

 We are working on EMMC(MMC1) boot on a custom board and could not make it. We used uniflash to flash the image to EMMC(MMC1) successfully. But after reboot, I tested EMMC clk/cmd pin by scope. There is no output at all.  

 1.  For EMMC, does the GPMC_WP0 pin is required to set to low.  Does the  ROM(PBL) will check this Pin (Used as SD/MMC card insert detection).  

 2. We are aware of the pin for EMMC(MMC1) for boot is special according to Tables 5-32 or 5-33 in the TRM.  Does TI have any reference design? 

 3. We did not connect the data pin correctly, I am looking for a work around for this. Does AM4378 has any interface and internal flash,  I could use to flash MLO to boot from. 

Thanks

Wayne